The present invention relates to a contact arrangement for vacuum switches having cup-type contacts which are arranged coaxially opposite each other, are movable relative to each other in the axial direction and each of which have hollow-cylindrical contact supports which contain slots inclined to the longitudinal axis in the same sense, the contact supports each supporting a contact plate for providing electrical contact.
As is well known, the maximum breaking capacity of vacuum switches is given by the maximum values of the current which can be switched off safely and the returning voltage after the arc is broken, and can be influenced favorably by a magnetic field which is directed parallel to the direction of the arc current. A contraction of the arc which leads to an increase of the arc voltage and the power conversion connected with this voltage can be prevented by a coaxial magnetic field in the vicinity of the arc between the open contacts. For this purpose, a coil cylindrically enclosing the switching chamber can be provided with these so-called axial field contacts. The coil is connected in series electrically with the switch contacts and builds up an axial magnetic field which depends on the current and which permeates the gap between the coaxial contacts in the axial direction. For increasing the field strength in the contact gap, the coil can also be constructed with two layers and the turns can be made to run back and forth in the manner of a helix. The manufacture of such vacuum switches, however, is relatively expensive.
In one known embodiment of a contact arrangement for vacuum switches with cup-type contacts which are arranged coaxially and opposite each other and are movable in their axial direction relative to each other, the axial magnetic field between the open contacts is generated by coil turns which are made by slots in the two contact carriers. These slots have the same direction of rotation in both contacts. The end faces of the contact carriers facing each other are each covered by the rim of a substantially disk-shaped contact surface or plate. Between the contact plate and the bottom of the contact, a support body of mechanically strong and electrically poorly conducting material can further be provided. The contact plates are generally provided with radial slots for suppressing eddy currents. See, e.g., DE-OS No. 32 27 482.